<p>Photoreactive Ag(I) complexes of <i>p</i>-toluenesulfonate ions with the unsymmetrical alkene <i>trans</i>-1-(4-acetoxyphenyl)-2-(2-pyridyl)ethylene <b>1</b> is reported. The crystal [Ag(<i>p</i>-tol)(<b>1</b>)<sub>2</sub>]•(H<sub>2</sub>O) (<i>p</i>-tol = <i>p</i>-toluenesulfonate) undergoes a [2 + 2] photocycloaddition reaction in quantitative yield to afford the head-to-tail (ht) photoproduct <i>rctt</i>-1,3-bis(2-pyridyl)-2,4-bis(4-acetoxyphenyl)cyclobutane <b>2</b> regioselectively. The aromatic rings of the olefin participate in face-to-face π–π interactions and adopt an anti-conformation to position the carbon–carbon double bonds (C = C) in a suitable orientation to undergo photoreaction between neighboring complexes.</p
